US2294977A - Heater - Google Patents

Description

Sept 8 1942- J. N. GARRlsoN Erm. l2,294,977

HEATER l I Filed July 2, 1940 2 Sheets-Sheet l www ATTORNEYS Patented Sept. 8, 1942 UNTED rsi' sin@ HEATER Application July 2, 1940, Serial No. 343,612

11 Claims.

This invention relates to heaters and more particularly to an improved iiuid heaterV especially adapted forl heating oil for refining purposes, water for the production of steam,- gases, etc.

In fluid heating, and reierence will be made herein particularly to oil heating, it is common practice to provide a structure comprising a heater chamber or chambers in which are disposed tubes through which ows the uid to be heated. Some of these tubes are usually arranged to be heated mainly by either direct or reflected radiant heat rays from the heat source While other tubes are heated mainly by convection from the gases forming the products of combustion. These tubes are referred to as the radiant tubes and the convection tubes respectively and usually the oil flows through these tubes in series, the radiant tube bank being separated from the convection tube bank by several rows of tubes which are heated both by radiation and convection and which are called compensation tubes. Their function is to compensate for the relatively. high temperature differential which usually exists between the radiant and convection tube banks.

Our present invention relates to improvements in uid heaters having radiant tubes and convection tubes. It is among the objects of our invention to provide a heater of an improved dez sign whereby the heating eiciency is increased and the cost of construction and upkeep reduced. Other objects of our invention include: the provision of a heater of the type described which comprises only four walls and a base and which does not require any suspended roof or arch structure; the provision of a heater having a convection section such that the mass Velocity of gases passing therethrough will remain substantially uniform regardless of reduction in volume of the gases due to lowering of the temperature thereof caused by absorption of heat by the medium being conveyed in the tubes; the provision of a heater of such design that the flow of products of combustion will be substantially vertical and parallel to the end walls of the heater; the provision of a heater of the type described having a minimum of angular intersections of the refractory walls whereby the V number of corners or cold zones 1s reduced; the

provision of a heater which may be operated under relatively low draft due to unrestricted flow of products of combustion therethrough; theprovision of a heater structure which're'quires a minimum of material for ai heater of given capacity; the provision of a heater in which the end wall area is reduced to a minimum consistent with combustion volume requirements; the provision of a heater having a radiant heating section of such design that the number of reflections required in the course of a radiation, from its point of liberation to the surface when it is absorbed, is reduced to a minimum; the provision of a heater which may be adapted for iuse with either gaseous, liquid or solid fuel without substantial change in the overall e'iciency thereof; the provision of an arrangement of Walls and tubes in a heater whereby very efcient radiant heat transfer is effected and the capacity of the heater increased; and the provision of an extremely simple, easily constructed, and rugged heater structure.

The above and other objects of our invention will appear from the following description of several forms thereof, reference being had to the accompanying drawings, in which- Figure 1 is an illustrative prospective view of a heater embodying our invention. Y

Figure 2 is a vertical cross-sectional view taken substantially on line 2 2 of Figure 1.

Figure 3 is a horizontal cross-sectional view taken on line y3-3 of Figure 2.

Figure 4 is a vertical cross-sectional view generally similar to Figure 2 but showing a double type heater.

Figure 5 is a horizontal cross-sectional View taken on line 5-5 of Figur-e4, illustrating the sectional dampers for regulating the flow of the products of combustion into the stack.

Reference to Figures l and 2 will disclose that the illustrated form of our heater is generally triangular in vertical cross-section, the preferred shape being that of a right angle triangle having its base shorter than the adjacent side. YAs will appear later, the double heater of Figure 3 is, generally speaking, made up of two single heaters arranged in back to back relation.

The base or floor of the heater (Fig. l) is laid on a suitable foundation l and vertical columns 2 are suitably mounted on the base I and support the vertical tube carrying wall 3 which is made of any suitable refractoryV material, for example iirst quality monolithic insulating re' fractory. The sloping wall 4 is supported by correspondingly sloping columns 5, connected at their upper ends to the' columns 2 by means of connecting members S. The wall 4 is suspended on the columns 5 by any suitable means and is preferably made of rst quality refractory brick backed up b`y suitable insulation indicated at l.

rlhe end walls 8 and 9 complete the heater enclosure and these walls are also lined with refractory material.

In the upper corner or near the apex of the triangular heater chamber, adjacent the pointl of convergence of the Walls 3 and 4, is disposed the bank of convection tubes IIB. Oil or other fluid to be heated enters these tubes through the inlet pipe II. The two rows of tubes indicated at I2 and I3 are disposed between the convection bank IIJ and the radiant bank I4 and are termed compensation tubes. These tubes I2 and I3 receive both convection and radiant heat.

Oil which has passed through the radiant bank I4 may be removed through the pipel I 5 and heat is supplied to the heater chamber by means of the spaced gas burners I6 which discharge their flames adjacent and substantially parallel to the radiant wall 4 and toward the outlet slot or opening 20 between the tube carrying wall 3 and radiant wall 4. As an alternative source of heat we provide oil burners I'I which direct their flame horizontally and parallel to the base I8 of the combustion chamber. As seen at I9, this base or floor of the chamber is preferably rounded to assist in directing the ame and products of combustion from the oil burners I'I upwardly to and along the radiant wall surface 4.

The entire top of the heater structure is an elongated outlet 20 extending across at the apex of the converging Walls of the heater chamber, through which the products of combustion pass and which is connected to the breeching 2 I which in turn is connected tothe stack 22.

When firing the heater with gas the series of spaced burners I8, one of which is seen in crosssection in Figure 2, direct their flames close to and along the surface of the sloping refractory wall 4. As the point of highest temperature of the flame from the burners is adjacent the burners themselves it will be observed that the greatest radiant heatwill emanate from the part of the wall 4 which is spaced the greatest distance from the tube wall 3. The lowermost of the radiant tubes I4 are spaced a maximum distance from this zone of greatest radiant heat and the heater chamber is designed and proportioned so that the hottest temperature zone of the wall 4 is as close to the surface of the tubes I4 as is consistent with the ability of the tubes to withstand heat. The most effective heating is obtained by having the radiant wall 4 converge toward the wall 3 and its bank of tubes I4. The wall 4 naturally becomes progressively cooler toward the upper portion thereof but, due to the inclination of the wall 4, the cooler portions become progressively closer to the tubes I4 and thus sub-w stantially uniform radiant heat is applied to the ybank of tubes I4 over their entire area and the maximum radiant heating eciency is obtained in a minimum of space.

The products of combustion on their way to the stack 22 pass through the tapering convection tube bank I where heat is transmitted to the oil in the tubes by convection. The progressive reduction in area of the gas passage through the convection bank is such that the cross-sectional area of the heater in any horizontal plane is less than the cross-sectional area of the heater in a plane at a lower elevation. This progressive reduction in areas is such that the mass velocity of gases passing vertically through the convection section will remain substantially uniform in ratio to the reduction in volume of the gas due to lower temperature thereof caused by the absorption of heat by the medium being conveyed in the tubes in the convection section and the heat loss by radiation through the walls.

The convection section is so designed that the cross-sectional area determining the velocity of the gases passing therethrough is less for each succeeding row of tubes in the path of the gases, the decrease in area being accommodated to the temperature and volume reduction of the gas which results from absorption of heat therefrom by the tubes. The design of our heater greatly facilitates this control of the velocity of the gases in the convection section and makes possible the most desirable flow of hot products of combustion through the convection section without the interposing of any angles, corners, baffle walls or the like.

With respect to the radiant wall 4 it will be observed that it has its radiant surface all in one plane, corners being completely eliminated. Such corners or angular intersections of walls are particularly objectionable in radiant walls, not only because such corners ordinarily are low temperature zones and create secondary or eddy gas currents, but also because they increase the number of reflections required in the course of a ray from its point of origin to the tube surface with a resulting heat loss at each reflection. Withour triangular heater structure the gas burners are disposed close to the wall thus creating a high average wall temperature and an eflicient radiant wall. This wall operates at maximum efficiency because it has its coldest temperature zone closest to the radiant tube bank. No obstacles are interposed in the path of the products of combustion, other than the tubes I0, I2 and I3, and thus the draft required for proper operation of the heater is reduced to a minimum.

In order to regulate and equalize the flow of products of combustion through the heater we preferably provide a series of transverse dampers 23 along the top outlet 2!! of the heater. By adjusting these dampers the flow of products of combustion can be effectively regulated so that substantially equal heating occurs through the entire length of the heater structure.

Another very advantageous feature of our improved heater structure, as shown in Figures 1 to 4, is that the surface of the end walls of the heater chamber is relatively small. As the ends are low temperature zones which do not add materially to the heating efficiency of the furnace, it will be understood that anything which tends to reduce the area of the walls results in denite advantages.

In the above remarks reference has been made particularly to operating the furnace by gas burned in the burners I6. However, if gas is not available oil may be burned in the burners I 1. As is well known, a certain clear area is required in front of an oil burner in order that the oil may be completely consumed before it strikes a Wall or other surface. With our arrangement the base or floor I8 is sufficiently long to permit the proper combustion of the oil and the products of combustion are then directed up along the sloping wall 4 which they heat and from which radiant heat is directed against the tubes I4. Powdered coal may be similarly burned in our heater and,in some instances, solid fuel may be burned on suitable stoker or grates at the base of the triangular structure.

From the above description of our invention it will be observed that our heater not only provides a most effective means for applying radiant heat tothe bank'of tubes I4 but also. provides a most ecient and eifective means forv applying convection heat to the tubes l; In combination with this improved heating efficiency our structure is free from baies or other elements which interfere with the liow of products of combustion, is extremely simple, and has a minimum end wall area for a given heating capacity.

In Figure 4 we have illustrated a double heater which, as noted above, comprises essentially a pair of heaters as shown in Figure 2 combined in a single structure in back toA back relation. The sloping radiant walls 24 and 25 join at their upper ends to form the apex of the triangular structure. A shorter wall 25 extends up from the base 2l to a point short of .the outlet 28. One bank of radiant tubes 29 is supported on one side of the Wall 26 and receives its radiant heat from the wall 24 and another bank of radiant tubes 3!) is supported on the oppositeV side of the wall 26.

and receives its radiant heat from the wall 25.

The convection bank or banks of tubes 3l is disposed between the converging upper portions 24a and 25a of the walls 24 and 25 and, due to the progressive restriction of the gas passage through the convection section, the advantages set forth above are also obtained in the structure of Figure 3. A series of gas burners 32 are arranged along the bottom of the wall 2li and are adapted to heat same, while similar burners 33 are disposed along the bottom of the wall 25. These burners 32 and 33 heat the walls 24 and 25 in the same manner as the burners l heat the wall 4 and the walls 24 and 25, due to their angular relation to the radiant tube banks 29 and 30, apply radiant heat in a most uniform and efficient manner. The dampers 34 are mounted on individual shafts 35 provided with operating handles 36 and serve to equalize the ow of products of combustion vertically through the combustion chambers3'l and 38 into the breeching 39 and the stack 4B. These dampers 34 are shown in plan View in Figure 4 and it will be seen that by individually setting these dampers any slight variations in flow along the length of the heater may be adjusted.

Our improved heater not only results in a simple and more eicient apparatus but also does not require as high a chimney as would be required for a conventional heater capable of the same heat load. This is due to the fact that all of the walls of the convection section of our preferred form of heater are a continuation of the combustion chamber walls in their respective planes. Thus, eddy currents and changes in direction of the travel of the gases are eliminated and this results in a lower draft requirement to secure the necessary draft at the burners with a given draft loss through the convection section.

As the outlet from the convection section covers the entire length of this section the products of combustion from the spaced gas burners adjacent the radiant walls will pass vertically upwardly through the furnace. Furthermore, by making each of the convection section walls a direct continuation of its companion combustion chamber or radiant section wall, with each wall in a single plane from the burners to the outlet opening of the heater, less material is required for a heater of given capacity, anda supporting structure of extremely simple design results, thus reducing the cost of design and construction. A structure of such design increases the percentage of steel work and walls which can be fabricated in the shop, thus reducing erection costs. Also, due to its simple and efficient design, our imtail it will be understood by those skilled in the` art that variations and modifications may be.

made. without departing. from the spirit of our invention. We do not, therefore, wish tobe limited to the particular structures and. arrangements herein shown and described but claim' asy our invention all embodiments thereof coming within the scope of the appended claims.

We claim:

1. A heater of the type described including a pair of walls arranged in converging relation, walls completing the heater enclosure, a bank of radiant tubes disposed adjacent the surfaceof one of said pair of walls, means for discharging burning fuel substantially parallel and closely adjacent to the surface of the other of said pair of walls, and a bank of convection tubes disposed at the apex between said pair of converging walls.

2- In a heater of the type described, a structure including a vertical wall, a sloping, angularly disposed, wall having its upper edge close to said vertical wall but spaced therefrom to provide an:

outlet, walls connected to said vertical and sloping walls to form a heater chamber, a bank of convection tubes disposed in the apex between said vertical wall and said sloping wall adjacent said outlet, a bank of radiant tubes supported on and adjacent to the surface of said vertical wall, and fuel burners disposed adjacent the edge of said sloping wall remote from said outlet and adapted to direct their flames adjacent to and. along the surface of said sloping wall toward said outlet.

3. In a heater of the type described, a structure including a vertical wall, a sloping, angularly disposed, Wall having its upper edge close to said vertical wall but, spaced therefrom toprovide an outlet, walls connected to said Vertical and sloping walls to form a heater chamber, a

bank of convection tubes disposed in the apex between said vertical wall and said sloping Wall` adjacent said outlet, a bank of radiant tubes supported on and adjacent to the surface of said vertical Wall, a fuel burner disposed adjacent the edge of said sloping wall remote from said outlet and adapted to direct its name adjacent to and along the surface of said sloping wall toward said outlet, flue means for conveying away said products of combustion from said heater, and adjustable damper means between said heater and flue means.

4. In a heater of the type described, walls defining a heater chamber substantially a right triangle on every transverse vertical plane therethrough and substantially rectangular on every horizontal plane therethrough, any horizontal plane being smaller than another horizontal plane taken below said first named horizontal plane, radiant tubes in said chamber disposed along the vertical wall of the right triangle, convection tubes disposed in an apex of said triangle, and means for heating the hypotlienuse wall opposite said radiant tubes.

V5. A heater of the type described having its vertical transverse cross-section substantially in the form of a right triangle, the base of the triangle being shorter than the vertical side thereof and the hypoth'enuse comprising a wall having a, refractory inner surface, radiant tubes disposed adjacent the vertical side of the right triangle, convection tubes disposed in the apex between the hypothenuse side and said Vertical side, and means for heating the refractory sur-V face of said hypothenus'e side wall.

6. In a fluid heater of the type described, walls enclosing a heater chamber, two of said walls being disposed in opposed upwardly converging relation and having an outlet therebetween'adjacent their point of convergence, a burner for applying heat to one of said walls at a point removed from said point of convergence, the burner being positioned to direct llame and products of combustion parallel and closely adjacent to said wall toward said outlet, a bank of radiant tubes adjacent the other of said two walls, a bank of convection'tubes supported in the apex between said two converging walls adjacent said outlet, and fluid conducting connections between said banks of tubes.

7. In a iluid heater, walls defining a heater chamber of triangular cross-section, an outlet opening at the apex between the joining edges of two of said walls which define said triangular cross-section, a bank of radiant tubes on one of said two walls, and means for heating the other of said two walls to a temperature which is greatest at the point most remote from said radiant tubes, said means including a burner disposed near the edge of said wall remote from said apex opening to direct flame and products of combustion parallel and closely adjacent to said wall and a bank of convection tubes in the apex between said two walls adjacent said outlet opening.

8. In a heater of the type described, walls dening a heater chamber of triangular vertical cross-section, one side of the triangle being the base of the chamber and the oth'er two sides sloping oppositely toward each other and having an outlet opening at their apex, a central tube supporting wall extending vertically upwardly from said base to a point below said outlet, banks of radiant tubes supported on opposite sides of said central wall, a bank of convection tubes in said apex, and means for heating said sloping side walls whereby the greatest heat is applied adjacent their lower edges,

9. In a heater of the type described, walls dening a heater ch'amber of triangular transverse vertical cross-section, one side of the triangle being the base of the chamber land the other two sides sloping oppositely toward each other and having an outlet opening at theirapex, a central tube supporting wall extending vertically upwardly from said base to a point below said outlet, banks of radiant tubes supported on opposite sides of said central wall, a bank of convection tubes in said apex, means for heating said sloping sidewalls whereby the greatest heat is applied adjacent their lower edges, and damper means in said outlet opening for controlling the low of products of combustion therethrough.

10. In a heater of the type described, a 'structure including a vertical wallra sloping, angularly disposed wall having its upper edge close to said vertical wall but spaced therefrom to provide an outlet, walls connected to said vertical and sloping walls to form a heating chamber, a bank of convection tubes disposed in the apex between said vertical wall and said sloping wall adjacent said outlet, a bank of compensation tubes disposed immediately below said convection tubes, a bank of radiant tubes supported on and adjacent the surface of said Vertical wall, and a fuel burner disposed adjacent the edge of said sloping wall remote from said outlet and adapted to direct its flame adjacent to and along the surface of said sloping wall toward said outlet.

11. A heater of the type described including a pair of walls arranged in converging relation, walls completing the heater enclosure, a bank of radiant tubes disposed adjacent the surface of one of .said pair of walls, means for discharging burning fuel into the closure, means for directing the products of combustion of said burning fuel substantially parallel and closely adjacent to the portion of the other of said pair of walls from which heat will be reflected to said bank of tubes, and a bank of convection tubes disposed in the apex between said pair of converging walls.

JAMES N. GARRISON. JOHN H. HENZEL.

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